Keyswitch

ABSTRACT

An electromechanical switch that includes a floating contact suspended in an elastic material above a fixed contact is disclosed. Finger pressure compresses the elastic material forcing the floating contact to make electrical contact with the fixed contact completing the switch circuit.

United States Patent [19] Novak 5) May 8, 1973 [54] KEYSWITCH Primary Examiner-Robert K. Schaeffer Assistant Examiner-William J. Smith t [75] Inventor Phillip] Noni, Granger U ah Anomqxenneth T. Grace et a. [73] Assignee: Sperry lull Corporation, New

York, N.Y. .7 g Y a 22 Filed: Dec. 21, 1911 AB TRAC [211 App. Nod 212,015 An electromechanical switch that includes a floating contact suspended in an elastic material above a fixed a contact is disclosed. Finger pressure compresses the [52] US. Cl. .3001! G, 200/ I59 B elastic material forcing the floating contact to make 51 Int. Cl. .JIllh ammo": 9/04 electrical Contact with the fi Contact completing [58] Field of Search ..2oo/|s9 3, I68 0;

[56] References Cited 2 Claims, 7 Drawing Figures UNITED sures PATENTS 2,877,324 3/1959 Oshry ..200/l68 0 PAIENIEUM W Fig. 5

KEYSWITCH BACKGROUND OF THE INVENTION Keyswitches associated with the keyboards of electronic data processing systems are available in many designs see Keyswitches and Keyboards, EEE, November 1970, pages 64 73. Recent developments include printed circuit keyboards having keyswitches that include pressure sensitive materials whose re-' sistivity decreases with applied pressure to make electrical interconnection as in the K. Nyhus et al. U.S. Pat. No. 3,503,031 and two electrical conducting layers separated by an apertured electrical insulator wherein under applied pressure one layer is forced through the aperture to make electrical contact with the other layer as in the M. Krawinowski US. Pat. No. 3,308,253. The present invention is considered to be an improvement over such known arrangements using fewer components while providing desirable operator feedback.

SUMMARY OF THE INVENTION The present keyswitch includes an insulating base and a superposed key both sandwiching a fixed contact and a floating contact in the space therebetween. An elastic material fills the space resiliently restraining the floating contact above and out of electrical contact with the fixed contact, both of which contacts have associated leads extending through the base. Finger pressure on the key compresses the elastic material forcing the floating contact into electrical contact with the fixed contact completing the electrical switch circuit. Alternative configurations include two fixed contacts and the floating contact.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a keyswitch of the present invention.

FIG. 2 is a sectional view of an unstressed keyswitch illustrating the internal construction thereof.

FIG. 3 is a sectional view of the stressed keyswitch of FIG. 2.

FIG. 4 is a sectional view of another embodiment of the present invention.

FIG. 5 is a sectional view of a further embodiment of the present invention.

FIG. 6 is a sectional view ofa base that may be incorporated in the keyswitch of the present invention.

FIG. 7 is a sectional view of a still further embodiment of the present invention as mounted on a keyboard panel.

DESCRIPTION OF THE PREFERRED EMBODIMENT With particular reference to FIG. I there is presented an isometric view of keyswitch 10 of the present invention. Keyswitch 10 includes key 12 and base 14 sandwiching body 16 therebetween. Base 14 is preferably an insulating material ridigidly supporting lead 18 and lead 20 for coupling to the external electrical switch circuitry. Key 12 may include the desired alphanumeric symbol as required by the particular application concerned. It can be seen that body 16 completely encompasses the space between key 12 and base 14 forming an airtight, solid enclosure about the internal electrical components.

With particular reference to FIG. 2 there is shown a sectional view of keyswitch 10 illustrating the internal construction within body 16 substantially comprising an elastic potting material 22 that resiliently suspends floating contact 24, fixed contact 26 and flexible lead 28 therein. It can be seen the keyswitch 10 includes an insulating base 14 and a superposed key 12 both sandwiching a fixed contact 26 and a floating contact 24 in the space therebetween. Elastic material 22 fills the space resiliently restraining the floating contact 24 above and out of electrical contact with the fixed contact 26 both of which contacts have associated leads 20 and 18, respectively, extending through the base 14. This illustrates the relationship of the internal electrical components of keyswitch 10 under the unstressed condition, i.e., when no finger pressure is applied to key 12.

With particular reference to FIG. 3 there is illustrated the relationship of the internal electrical components of keyswitch 10 under the stressed condition, i.e., when finger pressure is applied to key 12. As stated with respect to FIG. 2, in its unstressed condition elastic material 22 fills the space between key 12 and base 14 resiliently restraining the floating contact 24 I above and out of electrical contact with the fixed contact 26. However, as illustrated in FIG. 3 when finger pressure is applied to key 12 the elastic material 22 is compressed forcing the floating contact 24 into electrical contact with the fixed contact 26 completing the external electrical switch circuit between leads 18 and 20.

With particular reference to FIG. 4 there is presented a sectional view of another embodiment of the present invention. In this embodiment keyswitch 40 includes an insulating base 44 and a superposed key 42 both sandwiching fixed contacts 46 and 48 and a floating contact 44 in the space therebetween. As in the em bodiment of FIGS. 2, 3, elastic material '52 resiliently restrains the floating contact 44 above and out of electrical contact with the fixed contacts 46 and 48, both of which contacts have associated leads 54 and 56, respectively, extending through the base 44. Finger pressure on key 42 compresses the elastic material 52 forcing the floating contact 44 into electrical contact with the fixed contacts 46 and 48 completing the external electrical switch circuits through their associated leads 54 and 56, respectively. .1

With particular reference to FIG. 5 there is presented a sectional view of a further embodiment of the present invention. In this embodiment keyswitch 60 includes an insulating base 64 and a superposed key 62 both sandwiching a fixed contact 66, a floating contact 68 and a flexible lead 70 therebetween. Floating contact 68 further includes a downwardly extending, pointed contact 72 for making electrical contact with fixed contact 66. Elastic material 74 resiliently restrains the floating contact 68 out of electrical contact with the fixed contact 66, both of which contacts have associated leads 76 and 78, respectively, extending through the base 64. Finger pressure on the key 62 compresses the elastic material 74 forcing the floating contact 68 and its associated pointed contact 72 into electrical contact with fixed contact 66 completing the external electrical switch circuit associated therewith.

Although such is not a pertinent part of the present invention many methods may be utilized to secure the keyswitch of the present invention to the keyboard panel with which the keyswitch is associated. In one configuration the keyswitch could be fixed to the keyboard panel by a suitable adhesive on the base-topanel surface contact, or a threaded base could be utilized. One threaded base configuration could be that of FIG. 6 in which there is utilized the base 80 rigidly supporting fixed contact 82 and its associated lead 84 and theother lead 86 both of which pass therethrough. Base 80 has a threaded portion 88 and a suitable nut 90 for threadedly compressing a keyboard panel against flange 92.

In the alternative arrangement of FIG. 7 a keyswitch 100 could be enclosed within a bottom inside enclosure 102 and a top outside enclosure 104 which enclosures fit into each other in a telescoping arrangement. Enclosure 104 could be adhesively secured on the inside to the top surface of keyswitch 100 while a threaded portion of the base of keyswitch 100 could secure the entire assembly to the keyboard panel 106 by means of a nut 108.

In assembling, e.g., keyswitch 10 of FIGS. 2, 3 the following steps are recommended:

I l. Assemble the component parts of keyswitch 10 in a suitable mold incorporating the necessary jigs and fixtures to maintain the desired physical relationships between floating contact 24 and fixed contact 26. Floating contact 24 is held in a fixed, superposed, nonelectrical contact position above fixed contact 26 within body defining potting material 22, the outside contour of which is defined by the mold.

2. Next, potting material 22 is injected into the mold under slight pressure to completely fill all voids therein. In the preferred method the component parts of the switch 10 are first cleaned with a suitable solvent material to ensure adhesion between such component parts and potting material 22. A suitable cleaning material may be Dow Corning 1200 Primer purchased from Dow Corning Corporation, Electronic Materials Department, Midland, Mich. which is allowed to dry for approximately one-half hour while a suitable potting material may be Dow Corning 3110 RTV Eneapsulant mixed with the proper quantity of Dow Corning RTV Catalyst S.

3. Next, potting'material 22 is then allowed to cure at ambient, i.e., room, temperature for a period of approximately 24 hours.

4. Next, keyswitch 10 the body of which is defined by the cured potting material 22 is removed from the mold.

5. Next, keyswitch 10 is cleaned and any flashing is removed while any voids in the cured potting material 22 such as formed by the means for securing the component parts in their desired positions, are filled with potting material 22.

The potting material defining body of keyswitch 10 has a durometer hardness of approximately 30 forming an elastic body for normally resiliently supporting the floating contact 24 within the bodyof the keyswitch 10 above and out of electrical contact with the fixed contact-26 but restrainingly permitting the floating contact 24 to make electrical contact with the fixed contact 26 when compressed such as by slight finger pressure applied to key 12. is completed assem ly' orms an inexpensive electrical switch the operative parts of which are sealed from ambient contaminants such as moisture and dust.

What is claimed is:

1. An airtight keyswitch, comprising:

a rigid insulative base member;

electrically conductive first and second fixed leads rigidly supported by said base member; ,e

.an electrically conductive fixed contact rigidly supported by said base member and electrically coupled to said first fixed lead;

an electrically conductive floating contact;

an electrically conductive flexible lead electrically coupling said floating contact to said second fixed lead;

a key member spaced apart from said base member and sandwiching said floating contact therebetween;

an elastic potting material substantially completely filling the space between said key member and said base member for forming an airtight elastic body for said keyswitch and supporting said floating contact out of electrical contact with said fixed contact and restrainingly permitting said floating contact to make electrical contact with said fixed contact when'compressed by said key member.

2. An airtight keyswitch, comprising:

a rigid insulative base member;

electrically conductive first and second fixed contacts rigidly supported by said base member;

an electrically conductive floating contact;

a key member spaced apart from said base member and sandwiching said floating contact and said first and second fixed contacts therebetween;

an elastic potting material substantially completely filling the space between said key member and said base member for forming an airtight elastic body for said keyswitch and supporting said floating c'ontact out of electrical contact with said first and second fixed contacts and restrainingly permitting said floating contact to make electrical contact with said first and second fixed contacts when compressed by said key member.

t i III l 1! 

1. An airtight keyswitch, comprising: a rigid insulative base member; electrically conductive first and second fixed leads rigidly supported by said base member; an electrically conductive fixed contact rigidly supported by said base member and electrically coupled to said first fixed lead; an electrically conductive floating contact; an electrically conductive flexible lead electrically coupling said floating contact to said second fixed lead; a key member spaced apart from said base member and sandwiching said floating contact therebetween; an elastic potting material substantially completely filling the space between said key member and said base member for forming an airtight elastic body for said keyswitch and supporting said floating contact out of electrical contact with said fixed contact and restrainingly permitting said floating contact to make electrical contact with said fixed contact when compressed by said key member.
 2. An airtight keyswitch, comprising: a rigid insulative base member; electrically conductive first and second fixed contacts rigidly supported by said base member; an electrically conductive floating contact; a key member spaced apart from said base member and sandwiching said floating contact and said first and second fixed contacts therebetween; an elastic potting material substantially completely filling the space between said key member and said base member for forming an airtight elastic body for said keyswitch and supportIng said floating contact out of electrical contact with said first and second fixed contacts and restrainingly permitting said floating contact to make electrical contact with said first and second fixed contacts when compressed by said key member. 